Water heater

Abstract

A water heater includes a bypass that is formed, on the side of a water supply pipe, branching from a main water path and bypassing a part of the main water path, and a flow path switching unit (a valve and a stepping motor) that is formed at a branching portion of the main water path and the bypass. The flow path switching unit is controlled by a controller and that can selectively switch a flow path between the main water path and the bypass. A microbubble generator generating microbubbles is provided on the bypass, the microbubble generator including a water agitator portion, a compression portion and a decompression portion. When the controller determines that scale has built up, the flow path is switched to the bypass by the flow path switching unit, and water containing microbubbles is caused to flow inside the water heater.

What is claimed is: 
     
       1. A water heater comprising:
 a burner; 
 a heat exchanger heated by the burner; 
 a water supply pipe and a hot water delivery pipe that are connected to the heat exchanger respectively; and 
 a control unit controlling combustion by the burner, wherein the control unit is electrically connected to a temperature detection unit; 
 wherein 
 water passing through the heat exchanger is heated by the burner and heated water is delivered, and 
 when a temperature detected by the temperature detection unit provided on the hot water delivery pipe reaches a predetermined temperature due to heat rise after hot water delivery is stopped, the control unit determines that scale has built up inside pipes, and 
 a bypass branching from a main water path is formed on the side of the water supply pipe to bypass a part of the main water path, and a flow path switching unit is provided at a branching portion of the main water path and the bypass, the flow path switching unit being controlled by the control unit and being able to selectively switch a flow path between one of the main water path and the bypass, 
 a microbubble generator being provided on the bypass, generating microbubbles and including a water agitator portion, a compression portion and a decompression portion, and 
 the agitator portion houses a swivel wheel that rotates as a result of an inflow of water, the compression portion is communicatively connected to the agitator portion and serves as a tapered flow path whose diameter narrows progressively toward the downstream side, and the decompression portion is communicatively connected to the compression portion and serves as a tapered flow path whose diameter widens progressively toward the downstream side, and 
 when the control unit determines that scale has built up, the control unit uses the flow path switching unit to perform switching of the flow path so that the water passes through the bypass, and then water containing the generated microbubbles flows inside the water heater.